Low Level Operations - Issues

[vijay84]

I have a zip file uploaded in s3 bucket. I m fetching the content of zip in buffer format and passing it to zipper.unzip function. performed some editing in some files, now when I am trying to upload it back to s3 it should be in the buffer format.
Here as we are not getting it in buffer format, its OK. but I am not able to zip it again.
var cleanUnzippedFS = unzipped.memory();
zipper.zip(cleanUnzippedFS, function(zipped) {
zipped.save(finalKey.fileName + '.zip', function(error) {
if(error) {
console.log("ERROR: %s", error.message);
}
else {
console.log("The file is scanned and cleaned of executables");
}
});
});

Here after adding above code snippet to my code inside unzip the zipped instance is always comes as null.
Not sure how can will get this issue fixed, please help!!!